The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing polyester resins wherein the end groups of the polyester resin are modified with hydrophobic groups, which for example impart or assist in imparting a lower relative humidity sensitivity to the toner particles and enable toners with rapid admix characteristics. In embodiments, there are provided in accordance with the present invention toner compositions comprised of resin particles, pigment particles, and a polyester resin free of acid end groups and containing a hydrophobic end group, or groups, such as a siloxane, a fluorocarbon or halogenated hydrocarbon, which groups impart or assist in imparting a low relative humidity sensitivity, such as from about 1.0 to about 2.5 to the toner particles, and enable toners with rapid admix characteristics, such as less than 60 seconds. More specifically, in embodiments of the present invention, there is provided a toner comprised of pigment particles and a polyester resin containing end groups, and wherein the polyester is illustrated by the following Formulas I, II, or mixtures thereof in embodiments ##STR2## wherein R is an aliphatic, especially alkylene, group such as a hydrocarbon with from about 2 to about 45 carbon atoms, an alkyleneoxylated bisphenol, especially bisphenol A such as propyloxylated bisphenol A, cycloalkylene like a cyclohexylene, such as 1,4-dimethyl cyclohexylene; R' is an arylene with, for example, from 6 to about 30 carbon atoms group such as isophthalylene, terephthalylene or phthaloylene, an olefinic group such as vinylene, methylvinylene, or an aliphatic hydrocarbon such as alkylene like ethylene, propylene, butylene, penylene, hexylene, and the like; X represents the hydrophobic end group, such as a silane like a trimethylsilyl, triethylsilyl, or siloxane, such as dimethylsiloxane of weight average molecular weight of from about 200 to about 20,000 grams per mole, or a fluorinated hydrocarbon with, for example, from 1 to about 45 carbon atoms, such as trifluoromethyl, pentafluorethyl or octafluorpentyl, or other halogenated hydrocarbon such as tribromomethyl, chlorohexyl, the corresponding alkyl halogenated fluorinated hydrocarbons, and the like; and n represents the number of repeating segments.
The aforementioned toner compositions and developers thereof, that is the toner mixed with a carrier, display in embodiments a low relative humidity sensitivity for the toners thereof, which is desired, thus the triboelectric charge is stable to changes in environmental humidity conditions. Copiers and printers equipped with two component developers, that is a toner as one component mixed with the carrier as the other component, can exhibit a positive or negative triboelectric charge with a magnitude of from, for example, about 7 microcoulombs per gram to about 40 microcoulombs per grams. This triboelectric charge permits the toner particles to be transferred to the latent image of the photoreceptor with an opposite charge, thereby forming a toned image on the photoreceptor, which is subsequently transferred to a paper or a transparency substrate, and thereafter subjected to fusing or fixing process. In these development systems, it is important for the triboelectric charge to be stable under differing environmental humidity conditions such that the triboelectric charge does not change by more than from about 5 to about 10 microcoulombs per gram. A change of more than from about 5 microcoulombs per gram to about 10 microcoulombs per gram in triboelectric charge of the toner developer can cause nonuniform toned images or result in no toning of the photoreceptor, thus unbalanced density or gray scale is observed in the developed images, or no developed images at all result. Generally, humidity ranges may differ from less than about 20 percent in dry regions to more than about 80 percent in humid regions, and some geographical regions may exhibit fluctuations of up to from about 50 to about 80 percent humidity level within the same day. In such climates, it is important that the developmental triboelectric charge does not change by more than from about 5 microcoulombs per gram to about 10 microcoulombs per gram. As toner resins generally represent from about 80 percent to about 98 percent by weight of the toner, the resin sensitivity to moisture or humidity conditions should be minimized thereby not adversely affecting the triboelectric charge thereof. A number of toner polymeric resins utilized as toner compositions, such as for example styrene-acrylates, styrene-methacrylates, styrene-butadienes, and especially polyesters, contain from about 0.1 to about 2 percent by weight of moisture, and in some instances, the moisture content of polyesters may change from about 0.1 to about 4 percent by weight at humidity levels ranging from about 0 to about 100 percent, or preferably from about 20 percent to about 80 percent humidity. These changes in moisture content of the resin may have a dramatic adverse effect on the triboelectric charge of the toner developer. The relative humidity sensitivity of toner is customarily measured by first fabricating a toner comprised of a pigment, optional charge control agent and a resin, then admixing the toner from about 3 percent by weight to about 7 percent by weight with a carrier. The developer composition is then subjected to various humidity levels in a sealed chamber for a finite period of time, such as about 48 hours. The triboelectric charge is then measured for the same developer composition at differing humidity levels and analyzed by several methods, such as graphing the triboelectric charge as a function of humidity level and observing the regions in which dramatic changes occur. Another measuring method comprises dividing the aforementioned graphical interpolation of tribo versus humidity level in three regions, wherein region I is from about 0 to about 30 percent humidity, region II is from about 30 to about 65 percent humidity, and region III is higher than about 65 percent humidity to about 100 percent humidity. Since these measurements are cumbersome and require substantial time, the toner triboelectric charge can be measured after subjecting the toner developer composition to two humidity levels, such as 20 percent humidity and 80 percent humidity, and then calculating the relative sensitivity by taking the triboelectric charge ratio of the 20 to 80 percent humidity as given by the following ##EQU1## wherein RH is the relative humidity.
Thus, if the relative sensitivity is about 1.0, the toner composition is considered nonhumidity sensitive, whereas if the relative sensitivity is greater than from about 3, or greater than about 5, the toner composition is considered to be very humidity sensitive. It is generally believed that a number of polymeric materials exhibit relative sensitivity greater than 1.0, and in general, styrene butadiene, or styrene acrylate possess relative humidity sensitivity of greater than 1.0 and less than about 2.5, whereas polyesters generally possess a relative humidity sensitivity of greater than about 2.5 and less than about 5. Hence, an advantage of the styrene-acrylate or styrene-butadiene class of resins over polyesters is their lower relative sensitivity. Polyesters are known to display advantages over styrene based resins, such as low fixing temperatures of from about 120.degree. C. to about 140.degree. C., high gloss, such as from about 50 gloss units to about 80 gloss units, and nonvinyl offset properties. Therefore, there is a need for toner compositions comprised of a resin which possess many of the aforementioned advantages, such as low fixing of from about 120.degree. C. to about 140.degree. C., a high gloss, such as from about 50 gloss units to about 80 gloss units, nonvinyl offset properties, and in addition low relative humidity sensitivity, such as from about 1.0 to about 2.5. These and other advantages are attained in embodiments with the toner compositions of the present invention comprised of a pigment, optionally a charge control agent, and a modified polyester resin wherein the end groups are hydrophobic, and which toners exhibit low fixing of from about 120.degree. C. to about 140.degree. C., high gloss, such as from about 50 gloss units to about 80 gloss units, nonvinyl offset properties, and low relative humidity sensitivity, such as from about 1.0 to about 2.5.
Also, the aforementioned toner compositions usually contain pigment particles comprised of, for example, carbon black like REGAL 330.RTM., magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, or brown components, or mixtures thereof thereby providing for the development and generation of black and/or colored images. The toner compositions of the present invention in embodiments thereof possess excellent admix characteristics as indicated herein, and maintain their triboelectric charging characteristics for an extended number of imaging cycles, up to for example 1,000,000 in a number of embodiments. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes, including color processes.
There is also a need for toner compositions which possess desired triboelectric charge levels of, for example, from about 10 to about 40 microcoulombs per gram, and preferably from about 10 to about 25 microcoulombs per gram, and admix charging rates of from about 5 to about 60 seconds, and preferably from about about 15 to about 30 seconds, as determined by the charge spectrograph. There is also a need for low relative humidity toners, such as from about 1.0 to about 2.5 and preferably of from about 1.2 to about 2.2, as calculated by Equation 1, and wherein low minimum fixing temperatures are obtained such as from about 125.degree. C. to about 145.degree. C. with a broad fusing latitude such as from about 30.degree. C. to about 45.degree. C. These and other needs are achievable with the toners of the present invention.
Certain polyester toner resins are known, reference for example in U.S. Pat. Nos. 3,590,000 and 4,525,445, which illustrate a linear polyester comprised preferably of propoxylated bisphenol A and fumaric acid, and available as SPAR II.TM. from a number of sources such as Atlas Chemical Company. There is also disclosed in Japanese Patent Laid Open 44836 (1975), 37353 (1982), 109875 (1982) and 3031858-A (1991) and references therein, a linear polyester resin comprised of polybasic carboxylic acid, such as those derived from ethoxylated bisphenol A, cyclohexanedimethanol and terephthalic acid. Further, there is disclosed in U.S. Pat. No. 4,533,614, and, more specifically, U.S. Pat. No. 4,957,774 a linear polyester resin comprised of dodecylsuccinic anhydride, terephthalic acid, alkyloxylated bisphenol A and trimellitic anhydride as chain extenders.
Additionally, there is disclosed in U.S. Pat. No. 4,940,644, U.S. Pat. No. 5,047,305, U.S. Pat. No. 4,049,447, and Canadian Patent 1,032,804 a linear polyester comprised of an amorphous aromatic polyester derived from an arylene radical and diol, and specifically resins such as poly(neopentyl-terephthalate) comprised of terephthalate radical and neopentyl glycol. Also, there is disclosed in U.S. Pat. No. 4,525,445 a toner composition comprised of a linear polyester derived from fumaric acid, isophthalic acid and propoxylated bisphenol. Further, other toner compositions are known to contain linear polyester resins, such as those disclosed in U.S. Pat. No. 4,968,575 and U.S. Pat. No. 5,004,664, a linear polyester prepared from the ring opening polymerization of cyclic monomers, and U.S. Pat. No. 5,057,392, which discloses a blend of resins comprised of a crystalline and amorphous polyesters; and U.S. Pat. Nos. 4,543,313 and 4,891,293 wherein there are disclosed linear thermotropic liquid crystalline polyester resins. Other U.S. Patents relating to polyesters are U.S. Pat. Nos. 4,052,325; 3,998,747; 3,909,482; 4,4049,447; 4,288,516; 4,140,644; 4,489.150; 4,478,423; 4,451,837; 4,446,302; 4,416,965; 4,866,158; 5,153,301; 5,116,713; 5,043,242; 5,045,424; 5,049;646; 5,102,762; 5,110,977 and 4,837,394.
Developer compositions containing modified polyester resins with a polybasic carboxylic acid are known and illustrated in Japanese Laid Open Nos. 44836 (1975); 37353 (1982) and 109875 (1982); and also in U.S. Pat. No. 3,681,106, and branched or crosslinked polyesters derived from polyvalent acids or alcohols are illustrated in U.S. Pat. Nos. 4,298,672; 4,863,825; 4,863,824; 4,845,006; 4,814,249; 4,693,952; 4,657,837; 5,143,809; 5,057,596; 4,988,794; 4,981,939; 4,980,448; 4,960,664; 4,933,252; 4,931,370; 4,917,983 and 4,973,539. The resulting modified polyester resins by branching or crosslinking improve the hot-offset resistance only at a sacrifice of the low fixing temperature performance. In several of the aforementioned prior art references, there are disclosed polyester resins wherein the end groups are either an acid group, wherein acid numbers are reported, or hydroxyl groups. Therefore, the polyester ends are hydrophilic and possess poor relative humidity sensitivity, such as from about 3.5 to about 4.5, and different from those of the present invention wherein the polyester resins are modified to be comprised of hydrophobic end groups such as silanes, siloxanes, fluorocarbons or other halogenated carbons, and the acid content is avoided and not present, hence good to excellent relative humidity sensitivity are obtained such as from about 1.2 to about 2.5. The modification of the polyester end groups to hydrophobic types reduces the relative humidity sensitivity of the resulting toners while still retaining the favorable low fixing temperatures, such as from about 125.degree. C. to about 145.degree. C., and broad fusing latitude, as well as excellent admix such as about 60 seconds or less.
The modification of polyester resins based on terephthalates, such as described in the U.S. Pat. No. 5,391,452, results in polyesters that contain a hydrophobic end group which reduces the relative humidity of from about 2.8 (Comparative Example I) to about 1.8 (Example II) or to about 1.5 (Example III). Furthermore, there is also illustrated in the copending application that the modification of propoxylated bisphenol A based polyester toners reduces the relative humidity of from about 3.5 (Comparative Example IV) to about 2.1 (Example V).
Also, there is illustrated in U.S. Pat. No. 5,366,841, a toner comprised of pigment particles, optionally a charge control agent, and a polyester resin comprised of alkyl end groups, and wherein excellent dispersibility with waxes is disclosed.
Illustrated in U.S. Pat. No. 5,407,772 is an unsaturated linear polymer comprising: a reaction product comprising first residues of a first monomer, second residues of a second monomer and third residues of a third monomer, said first monomer being a diol having a molecular weight below about 200, said second monomer being selected from the group consisting of dicarboxylic acids and diesters, and said third monomer being different from said second monomer and selected from the group consisting of aromatic dicarboxylic acids and diesters; a concentration of said second residues ranging from about 3 to about 15 wt. %, based on a total weight of the polymer, and a concentration of said third residues ranging from about 40 to about 50 wt. % based on a total weight of the polymer; said polymer having a glass transition temperature ranging from about 52.degree. C. to about 61.degree. C.; U.S. Pat. No. 5,354,840 is a functional-amine polyester polymer comprising at least a first residue of a first monomer, a second residue of a second monomer and from about 0.1 to about 10.0 mole percent of a functional-amine residue of a functional amine, said polyester polymer being prepared by reacting the first and second monomers and the functional amine in an inert atmosphere, the functional amine having a functional group to facilitate polymerizing the functional amine and the first and second monomers, the functional-amine residue facilitating reaction of the functional-amine polyester in an organic peroxide crosslinking reaction system; and U.S. Ser. No. 100,937 now abandoned is a polyester resin having a monofunctional, unsaturated end group located on at least one end of the polyester chain.